Regular viewers of the channel will know that I'm a bit of a fan of a concept known as lateral
thinking, having spent many a Saturday morning as a kid in the early 80s watching grainy programs on
TV presented by a guy called Edward de Bono who went on to write best-selling books on
the subject. I mention this because every now and then during the course of my research work I come
across a concept that exemplifies the principles that Mr de Bono espoused. And the technology I'm
focusing on today is a perfect example. To the casual observer it may look like nothing
more than an interesting metallic structure on top of a tall building. But to Ibis Power, who
are the company that installed it, it's a fully integrated, multi-faceted system called Power Nest
that provides several complementary services and benefits to the building below, all of which can
vastly reduce energy costs and potentially act as a hub for a localized community electricity
grid network. So I thought I'd better get in touch with Ibis Power to find out a bit more about how
their installation works and why it could play a vital role in the green energy transition.
Hello and welcome to Just Have a Think.
Finding ways to harness the power of wind from the top of tall buildings is a challenge that
appears to be engaging the minds of developers all over the world at the moment. You may
for example have seen the recent video I made about a US company called Aeromine,
who are testing a prototype wind generation unit on the roof of a building in Detroit, Michigan.
To find out what makes this new Power Nest concept stand out from the crowd I caught
up with its inventor via Zoom recently. He's called Dr Alexander Suma and unlike many other
designers he didn't start out by thinking 'how can I make a wind turbine work on top of a tall roof?'
He engaged a much more lateral thought process along the lines of 'how can I squeeze every
ounce of available resource from an otherwise virtually unused flat surface at high level?'
Back in 2009 while training to become an architect and civil engineer,
Alexander was sitting in a classroom learning about sustainable construction and like all
good creative people he was doodling in his notebook while he was listening to the speaker.
By the end of the lecture he'd sketched out a blueprint for an integrated rooftop wind and solar
installation that, in his mind, would also need to be beautiful and architecturally sympathetic.
So that's all fine and lovely and everything but it also has to work in the real world doesn't
it? And that's where a lot of conceptual ideas like this tend to fall by the wayside. But when
Alexander started looking into the concept in more detail he found that wind has a very high energy
density and tends to flow faster the higher you go. He also learned that allowing air to
flow rapidly beneath an installation of solar panels has a significant beneficial impact on
their performance. Both those physical attributes play a pivotal role in the design of the PowerNest
system, but the lateral thinking doesn't stop there, as we'll find out a bit later in the video.
Dr Suma founded Ibis Power back in 2012 to develop the PowerNest concept to full commercialization,
and by 2016 with the help of a 1.7 million Euro grant from the European Commission,
the company had a full-scale prototype that could be used for testing and validation. And that's
a really key milestone in the journey of any start-up because it allows potential investors
to properly scrutinize the proposition to see if it can generate a decent return on their money.
A year later Ibis received some seed investment and won permission to install the prototype unit
on the top of a 10-storey residential building in the Dutch city of Utrecht, resulting in some
glowing testimonials from the people who lived in the block below. There were no vibrations and
no noise coming from the installation, and of course the energy bills of the residents were
significantly reduced. So, you know, everyone's a winner! But that was just a single unit. Alexander
knew it would be vital to make use of a full roof space to generate as much energy as possible and
realize his vision of a crowning architectural structure blending seamlessly into a building.
That first full roof installation came into reality in 2021 as a fully integrated component of
a new apartment block construction in Rotterdam, comprising three turbines and 144 solar panels.
Then just one year later the second project, twice the size of the first, came into being on the red
building that we saw at the start of the video. That one's located in Eindhoven and it consists
of four wind turbines and 296 solar panels. One of the key insights that Alexander's architectural
training revealed was the fact that most tall modern buildings, at least here in Europe anyway,
have common dimensions for their main structure. It's typically 5.4 or 7.2 metres. So each
PowerNest module is fabricated to be exactly 7.2 metres in length and width. And as any fan of dear
old Henry Ford will tell you, standardization allows for mass production which drives economy
of scale and keeps the price for the end user to a minimum. There will of course be some variations
on building dimensions from time to time, so the company also produces a range of simple steel
fillets that take up any gaps and maintain the architectural integrity of any new installation.
The second key insight is the fact that most tall buildings also have the same lining in
their façade, which means Ibis can use their standardized modules to facilitate extremely fast
and safe attachment to the top of the building. So now we're getting to the business end of the
project and we can consider those other lateral thinking innovations that I mentioned earlier.
The first and perhaps most obvious step in designing any new installation is to assess
which direction the main wind flow comes from and orientate your turbine modules to get the
maximum benefit from that airflow. But perhaps counter-intuitively, in the PowerNest design, that
does not mean placing the turbines right on the edge of the roof that's closest to that airflow.
To understand that slightly confusing logic let's just have a quick look at how air flows around a
tall structure using a computer-generated model based on the 70 metre tall Eindhoven building.
Urban environments like this have lower wind speeds and a lot of turbulence. Air
is forced upwards as it hits a tall building and then it tries to come into balance with the
high level prevailing wind up here at what's known as the shear line. As a result you get
one big mess of turbulent wind flow directly above the roof. Meanwhile down here at street
level there are high pressure zones in front and low pressure zones behind the building,
causing wind nuisance to pedestrians. It's the reason why you sometimes get a very unwelcome
blast of wind in your face when you walk around a corner in a city environment.
The PowerNest system has very carefully designed louvres at three different heights,
each of which is shaped to direct the wind towards low pressure zones that accelerate
the airflow across the roof of the building, effectively sucking air towards the exit side.
And here's how that design changes the airflow in the computer-generated fluid dynamics model. It's
quite a dramatic difference isn't it? Not only is there a huge reduction in the turbulent air above
the building, but the wind nuisance at the base of the building is also significantly reduced.
And if we zoom in on the roof itself you can see that the airflow velocity is indeed increased as
it moves across the PowerNest structure. And that's why the turbines are placed a certain
distance away from the roof edge, where the air is flowing at its fastest speed. Each turbine drives
an electrical generator with a maximum capacity of three kilowatts which it reaches at a wind speed
of around 12 metres per second. The acceleration effect that we've just looked at means it's quite
common for the installation to achieve wind speeds of around 11 or 12 metres per second,
although wind flows are obviously not steady most of the time so there will be variation there.
The second Innovation is to mount the solar panels at the top of the structure, some 4.8 metres above
the roof, and to give that structure an overhang of one metre out from the roof edge on all four
sides. The weight of the whole installation equates to between 120 and 140 kilograms per
square metre, which is the equivalent of having 12 to 14 centimetres of water on a roof, and that's
well within acceptable operational parameters. The benefits of configuring the system in this
way are threefold. Firstly, it leaves the roof surface empty so that any essential equipment can
be housed there as normal. Secondly, the overhang means the PowerNest system can effectively utilize
more than 100% of the surface area of the roof it sits on, and thirdly it means that the carefully
directed airflow across the roof can continuously cool the underside of the solar panels. As we've
discovered in previous videos on this channel, solar PV doesn't work so well when it gets hot,
which is ironic given that it derives all its power from direct sunlight!
By drawing that excess heat away from the underside, the PowerNest structure squeezes
between 10% and 15% more power out of each panel, which is a significant improvement. The next piece
of smart thinking is to use bifacial solar panels and to make all the internal cladding white to
maximize light reflections onto the bottom surface of each panel. Believe it or not that single
simple step of logic results in another 20 to 30 percent efficiency in solar power generation.
And as a final sort of cherry on the icing on the cake, so to speak, all future PowerNest
systems will include a specially strengthened structural rail integrated into the roof edge
of the overhanging louvre frame, supported by the triangular structure beneath.
The rail will house the cabling for the building's façade maintenance cradle. That allows full access
for cleaning every window on every side of the building, and when it's not in use the cradle will
park itself neatly up on the rooftop underneath the PowerNest. It's yet another piece of lateral
thinking by the system's designer that'll do away with the need for a roof mounted crane. And in the
space where that crane would normally sit there'll be enough room for an extra 48 solar PV panels.
According to Dr Suma when you put all those innovations together you end up with a system
that achieves double the power generation of an equivalent PV installation mounted
on a similarly raised structure, and between 6 and 10 times more than a system of panels
mounted directly to the roof surface. And in terms of levelized cost of electricity,
which I know you folks are always keen to hear about, the PowerNest system comes out at between
8 and 12 cents per kilowatt hour depending on the location based on a 25-year operating lifetime.
A key goal for Ibis Power in the medium term is to include a battery energy storage system
underneath future PowerNest installations so they can be seamlessly integrated into
community power generation projects that'll be popping up in urban environments all over the
world as part of our rapid transition away from centralized fossil fuel driven energy providers
and towards a more distributed smart grid model. The Eindhoven installation for example provides
85 percent of the tower's electricity and Alexander Suma believes very strongly that
the residents should be allowed to become the owners of their own energy facility.
Legislation didn't allow that on this project, but that will certainly change over time.
Ibis are now discussing projects from as far south as Portugal and Spain all the way up to the
countries of Scandinavia. And of course there are high-rise buildings in sunny and windy locations
over in North America and across the globe, so the future looks extremely bright and extremely busy
for this ambitious start-up. The next two projects are due for completion in the Netherlands in the
first half of 2023 and another three are slated for installation before the end of the year.
So what do you think? Do you like the architectural design of the PowerNest
system? Could you envisage something like this on a building near you in the coming years?
And what do you think about those new community energy projects? Are they
genuinely the way forward or do you think they may turn out to be an unattainable pipe dream?
As always let me know your thoughts in the comments section below. That's it for this
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